Abstract

The importance of vertical jumping in sport and
rehabilitative medicine is widely recognized. Despite the
ample use of jump tests to assess neuromuscular function,
the diVerential eVects of muscular activation (volitional
eVort) and strategy (countermovement magnitude) on
jumping performance have not been studied. The present
study aimed to investigate the diVerential eVects of countermovement
magnitude and volitional eVort on vertical jump
performance. Ten male participants performed a total of 60
countermovement jumps each with three diVerent countermovement
knee angles (50, 70 and 90°) and four eVort
levels (25, 50, 75 and 100% of maximal eVort). Kinematics
and Kinetics were recorded using Vicon System together
with a force platform. Electromyography of four muscles
was recorded. Results show that countermovement magnitude
and volitional eVort both aVect jump performance.
These eVects were synergistic for jump height (P < 0.001),
but antagonistic for peak ground reaction force (P < 0.001).
Interestingly, peak jump mechanical power was aVected by
volitional eVort, implying an increase from 31.26 W/kg at
25% to 41.68 W/kg at 100% of volitional eVort, but no
countermovement magnitude eVect was observed for 100%
of volitional eVort. This suggests that the apparent paradox
of larger ground reaction forces in sub-maximal as compared
to maximal jumps is due to the diVerent jump strategies.
Moreover, these results are relevant for jumping
mechanography as a clinical tool, suggesting that peak
power can be used to assess neuromuscular performance
even when countermovement magnitude varies as a result
of age or pathology.